/Engine/Source/Runtime/GeometryCore/Public/DynamicMeshEditor.h
Project the two triangles of the quad onto a plane defined by the ProjectionFrame and use that to create/set new shared per-triangle UVs. UVs are translated so that their bbox min-corner is at origin, and scaled by given scale factor
void SetQuadUVsFromProjection ( const [FIndex2i](API\Runtime\GeometryCore\FIndex2i) & QuadTris, const [FFrame3d](API\Runtime\GeometryCore\FFrame3d_1) & ProjectionFrame, float UVScaleFactor, const FVector2f & UVTranslation, int UVLayerIndex )